The present invention relates to a wheel hub clutching mechanism, and more particularly to an improved wheel hub clutching mechanism to couple and uncouple a front wheel hub to and from a driveable front axle to selectively provide four-wheel drive or two-wheel drive.
In such a conventional wheel hub clutching mechanism as disclosed in U.S. Pat. No. 3,753,479 issued on Aug. 21, 1973, when a dial is turned to a lock position it moves an actuator cam to permit a primary strong compression spring to move a clutch element into mesh with the shaft driven pinion and when the dial is moved to a free position it moves the actuator cam to permit a secondary weaker return spring to move the clutch element out of mesh with the pinion. In other words, the weaker return spring is assembled in series with the strong compression spring on a common axis to be stressed when the clutch element is in mesh with the pinion so as to urge the clutch element toward disengagement from the pinion. With this assembling construction, the axial length of the clutching mechanism becomes large and the outer end of the clutching mechanism juts out laterally from the side of the vehicle body when the clutching mechanism is attached to a front wheel hub. Furthermore, in case the biasing force of the weaker return spring is unbalanced with the biasing force of the strong compression spring, engagement and disengagement between the clutch element and the pinion becomes unstable to make rattling noises.